The human immunodeficiency virus type 1 (HIV-1) integrase protein (IN) is a 32-kDa protein contained in the virus and following infection, it is released into the cytoplasm of infected cells. After virus-cell fusion, a process which promotes entry of the HIV-1 genome into an infected cell, the viral RNA is converted into double stranded DNA (cDNA). The viral DNA which becomes part of the preintegration complex (PIC) is eventually integrated into the host chromosomal DNA (Bukrinsky et al., 1993, Proc Natl Acad Sci USA 90, 6125-6129). Within the cytoplasm, IN catalyzes the first step of the integration process, namely the 3′-end processing in which an IN dimer removes a pGT dinucleotide from the 3′ end of each viral long terminal repeat (LTR) (Guiot et al., 2006, J Biol Chem 281, 22707-22719). Following nuclear import of the PIC, the host chromosomal DNA becomes accessible to the viral cDNA and the second step of the integration process, namely the strand-transfer step that is catalyzed by an IN tetramer takes place. This ordered sequence of events, centered on integration, is mandatory for HIV replication. Although each HIV-1 infected cell contains several copies of the viral genome, only a limited number of integration events per cell, mostly one or two, have been observed.
Due to its central role in HIV replication, the IN protein is an attractive target for antiviral therapy. Moreover, probably no cellular counterpart of IN exists in human cells and therefore, IN inhibitors will not interfere with normal cellular processes. However, only a few IN inhibitors have been identified to date.
Specific domains within viral proteins are responsible for their interaction with host-cell receptors and with other viral and cellular proteins enabling the completion of the viral propagation cycle within the host cell. Peptides derived from these binding domains may interfere with virus-host and virus-virus protein interactions and as such are candidates for therapeutic agents. Using this approach, short peptides that inhibit IN enzymatic activity were obtained following analysis of the interaction between two of the HIV-1 proteins, reverse transcriptase (RT) and IN. Screening a complete library of RT-derived peptides demonstrated that two domains of about 20 amino acids mediate this interaction. Peptides bearing these amino acid sequences blocked IN enzymatic activities in vitro (Oz et al., 2005, J Biol Chem 280, 21987-21996).
A limited number of IN inhibitory peptides have already been described. Using a combinatorial peptide library, a hexapeptide was selected that inhibited the 3′-processing and integration activity of IN (Puras et al., 1995, Proc Natl Acad Sci USA 92, 11456-11460). Based on the observation that this peptide also inhibited the IN from HIV-2, FIV, and MLV, it was suggested that a conserved region around the catalytic domain of IN is being targeted. An IN inhibitory peptide was also selected using a phage-display library (Desjobert et al, 2004, Biochemistry 43, 13097-13105). IN-derived peptides that interfered with its oligomerization also blocked its enzymatic activity (Maroun et al., 2001, Biochemistry 40, 13840-13848). Several other inhibitory peptides have been described in the last few years. Other studies described IN inhibitory peptides with anti-HIV-1 activity in some cell types (de Soultrait et al., 2003, Curr Med Chem 10, 1765-1778).
WO 2008/053478 describes IN inhibitory peptides derived from LEDGF/p75 protein. WO 2008/068765 discloses peptides comprising a fragment of the HIV-1 Rev protein which inhibit IN activity and virus replication. It was shown that the HIV-1 IN and Rev proteins can interact with each other intracellularly (Rosenbluh et al., 2007, J Biol Chem 282, 15743-15753), and speculated that the limited number of integration events observed in HIV-infected cells may result from regulated inhibition of IN enzymatic activity by the viral Rev protein. Zhao et al., 2003 (Bioorg Med Chem Lett 13, 1175-1177), discloses the peptide HLKTAVQMAVFIHNFKR (SEQ ID NO:1) corresponding to amino acid residues 171-187 of the IN, which block the protein's activity.
There is an unmet need for novel and improved compositions against HIV-1 infection, in a manner that is effective and specific to infected cells and safe to healthy cells, thereby reducing the side effects associated with known anti HIV medications.